[6] Not Crookes's.
"It was the opinion of Newton, and of many other distinguished philosophers, that this conversion was possible, and continually going on in the processes of nature, and they found that the idea would bear without injury the application of mathematical reasoning—as regards heat, for instance. If assumed, we must also assume the simplicity of matter; for it would follow that all the variety of substances with which we are acquainted could be converted into one of three kinds of radiant matter, which again may differ from one another only in the size of their particles or their form. The properties of known bodies would then be supposed to arise from the varied arrangements of their ultimate atoms, and belong to substances only as long as their compound nature existed; and thus variety of matter and variety of properties would be found co-essential. The simplicity of such a system is singularly beautiful, the idea grand and worthy of Newton's approbation. It was what the ancients believed, and it may be what a future race will realize."
In the closing words of his fifth lecture to the City Philosophical Society, Faraday said:—
"The philosopher should be a man willing to listen to every suggestion, but determined to judge for himself. He should not be biassed by any appearances; have no favourite hypothesis; be of no school; and in doctrine have no master. He should not be a respecter of persons, but of things. Truth should be his primary object. If to these qualities be added industry, he may indeed hope to walk within the veil of the temple of nature."
Many years afterwards he stated that, of all the suggestions to which he had patiently listened after his lectures at the Royal Institution, only one proved on investigation to be of any value, and that led to the discovery of the "extra current" and the whole subject of self-induction.
Faraday always kept a note-book, in which he jotted down any thoughts which occurred to him in reference to his work, as well as extracts from books or other publications which attracted his attention. He called it his "commonplace-book." Many of the queries which he here took note of he subsequently answered by experiment. For example:—
"Query: the nature of sounds produced by flame in tubes."
"Convert magnetism into electricity."
"General effects of compression, either in condensing gases or producing solutions, or even giving combinations at low temperature."
"Do the pith-balls diverge by the disturbance of electricity through mutual induction or not?"